Authors(s) and Affiliation(s)

Abstract

A series of flume experiments, using loose and water-worked gravel beds of narrowly graded grain sizes that were exposed to 6 h of crayfish activity under low-velocity flows, showed a substantial increase in the number of grains entrained by subsequent higher-velocity flows when compared with control runs in which crayfish were never introduced. Crayfish alter the topography of their substrate by constructing pits and mounds, which affect grain protrusion. When walking and foraging, they also alter gravel fabric by reorienting and changing the friction angle of surface grains. The increase in entrainment arising from disturbance by crayfish was shown statistically significant, with grain transport nearly twice as great. This study illustrates further the importance of acknowledging the impact of mobile organisms in conditioning the river bed when assessing sediment entrainment mechanics in the context of predicting bedload flux